I keep looking up this information and then losing track of it, so I'm posting it here for my own reference.
This command will turn off the monitor on a Linux box from the command line (sorta like what happens when you have your power saving options configured to do this automatically after a length of time):
xset dpms force offThe monitor turns off until you hit a keyboard button or move the mouse. With this info you could set up a keyboard shortcut to run this command and have something like a "lock screen button" on your netbook, to turn off the display on command and conserve battery life for a little bit longer than usual.
For a "lock screen button" that also locks the screen in addition to turning it off, a pair of commands like this may be handy:
xset dpms force off; xscreensaver-command --lock